The Verge published a video demonstrating how desktop mode and Office 2013 - a desktop application - work on Windows RT, the ARM version of Windows 8. The video showed a desktop mode that clearly didn't work well for touch, and even Office 2013, which has a rudimentary touch mode built-in, didn't work properly either. It looked and felt clunky, often didn't respond properly, and even showed touch lag.

You can, but Office and Explorer will be all you can run in desktop mode. Feel like running LibreOffice instead? Then you bought the wrong device.

[Of course in theory LibreOffice could devise a Metro version; they're working on Android support so compiling to ARM isn't the intractable part. Being enough touch-friendly to pass Microsoft's store rules while still being friendly to mouse & keyboard "docked" usage might be tricky!]